Description of the Prior Art
Aircraft which incorporate flaperons, particularly the instant invention, have numerous advantages over conventional aircraft having separate flaps and ailerons. These advantages become readily apparent upon examining the functions of these control surfaces. The lift of a wing, in part, is proportional to its coefficient of lift, its area and the square of its velocity as it moves through the air. Thus, at cruising speed, the wing area and the coefficient of lift required to maintain the aircraft's altitude is considerably less than that required at take-off or for slow-approach landing speeds. Sizing the wing for these latter conditions, which only exist for a few moments during a flight, would result in gross inefficiencies during the rest of the flight regime. In such case, the aircraft would have to carry the excess weight of the larger wing throughout the flight and would be subjected to a large drag penalty because of the greater wing surface area. The end results would be a reduced payload and higher fuel consumption. Thus, a major consideration in selecting the size of the wing is the aircraft's primary mission; i.e., conditions that the aircraft will face for the majority of its flight. This dictates the use of a wing area considerably smaller than that which take-off distance and landing speed would seem to demand.
This problem has been solved in the past by incorporating devices such as flaps into the wing, which can be extended rearward and downward as required, thereby effectively increasing wing area, and also increasing the coefficient of lift by increasing the mean camber line of the wing. This flap system is installed at the trailing edge of the wing.
Additional requirements for lateral or roll control also require that ailerons be incorporated into the trailing edge, reducing the space available for flaps. This loss of flap space on the trailing edge has been a particularly vexing problem on high-speed aircraft. Further difficulties have been engendered by the requirement for cruising speeds of 0.8 times the speed of sound, and higher. This has made necessary the use of swept wings, causing the ailerons which are mounted on the wing tips for maximizing the moment arm, to become ineffective at these high cruise speeds.
In certain cases, the phenomenon of aileron reversal occurs; i.e., when the pilot attempts to roll to the right, an aileron reversal causes a roll to the left. This results primarily from the facts that any practical wing is flexible and the dynamic loads at high speed are very large. When the aileron is deflected downward, for example, thereby attempting to increase the coefficient of lift by increasing the mean camber line, a resulting increase in dynamic pressure on the aileron causes the wing to twist. This twisting causes an overall decrease in the angle of attack of the wing tip, reducing the net force to zero, or until such time as there is a net downward force on the wing tip instead of a net upward force, thereby inducing the aileron reversal effect.
Such aileron reversal has required that a second set of ailerons be incorporated, further inboard from the wing tip, to provide roll control at higher speeds. Of course, the outer ailerons are still required for low speed flight. The net result is to further reduce the space normally allocated for flaps.
Thus, the design of a system efficiently combining the functions of an aileron with those of a flap is a highly desirable goal. Flaperon systems designed for such a purpose are far from new, as illustrated in U.S. Pat. Nos. 2,236,838 and 2,276,688, the closest prior art of which I am aware; however, none of the prior art systems are truly compatible with or adaptable to modern aircraft. Such prior art systems are complicated, generally unreliable, and heavy, or they occupy too much space in the wing, drastically reducing the fuel storage capacity. The inability to obtain high aileron response times has also been a problem in prior art systems. Therefore, a flaperon system compatible with state-of-the-art flap actuator systems would significantly improve the art by providing a considerable increase in the lift available for take-off and landing without increasing the overall size of the wing, as well as accommodating a considerable increase in aircraft take-off weight.